Signaling system



June 9, 1925. 1,540,797

P. B. MURPHY SIGNALING SYSTEM Filed May 8, 1920 2 SheetsSheet l Ifh i Q l i E I :HWVWL f H .l [I ii 3*: XL, 5 E a. I' ig i M-l l 2 l I x v. m. .j I l I l l In venfor;

Paul B. Mur oh June 9, 1925.

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SIGNALING SYSTEM.

' Application filed'may 8,

To all whom it may concem:

Be it known .that 1, PAUL B. MURPHY, a citizen of the United States, residing at Nyack, in the county of Rockland, State of a New York, have invented certain new and useful Improvements in Signaling Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to signaling sys-.

frequency much higher than that used to operate the ordinary type of low-frequency telephone ringer. Such telephone ringers generally operate in response to a. current having a frequencyof 16 to 20 cycles'per second, While the frequency commonly used over toll lines composited for telegraph and telephone operation is 135 cycles per second. To use this latter frequency it is necessary to employ a relay tuned to 135 cycles per second and responsive only to currents of approximately this frequency. To maintain satisfactorily this system-using a tuned relay, it is necessary that the tuned relay and associated relays be maintained in careful adjustment to prevent interference from low-frequency ringing current. or line impulses due to the telegraph service.

It is the object of this invention to provide an improved signaling system which may be maintained more satisfactorilythan the system above mentioned, and which is reliable in operation under all usual service conditions.

To attain this object, currentsof various frequencies are used for transmission over the toll line. Impulses of these currents are applied to the line sequentially in such a way that apparatus at the receiving end will respond to such impulses and to no others. By using frequencies within the 1920. Serial No. 379,705.

fill

plied in a predetermined manner, the possibility of false signals being received is remote.

The nature of the invention will clearly appear from the following specification and the annexed drawings, which show diagrammatically one embodiment thereof as applied to a telephone transmission line.

Fig. 1 and Fig. 2 show, respectively, a station X and a station Y, each with apparatus at the ends of a transmission line L,

and which when arranged end to end, with Fig. 1 at the left, represent a complete line. Since the line must be Worked in either direction, the apparatus at each end is similar. To generate the necessary signaling current of voice frequency, sending circuits S and S each composed of similar apparatus, are.

provided. The current is generated by means of vacuum tubes connected in a wellknown manner required to produce oscillating current. However, an other suitable means of producing currents of various frequencies, such as motor generator sets,'may be used. In the'particular circuit shown, alternate trains of'current waves of each frequency are produced by periodically varying the tuning ofthe oscillator circuit in a predetermined manner- One method of doing this, which is shown by the drawing and subsequently described, is to actuate a relay 3, by any convenient source of alternating or pulsating current ,i, of suitable frequency, such as 16 cycle ringing current.

Receiving circuits R, and R each composed of similar apparatus, are provided, which employ a vacuum tube for amplify ing and a filter circuit for separating the component currents of each frequency, which arrangement is old and well known in the 'be required when a signaling relay of sufiicient sensitiveness is used. In addition to the means just described for transmitting and receiving the currents of each frequency, there is also provided at each station a link circuit C, shown at station X, for connect- 7 ing to the line the telephones of the subscribers=-(such as 24, Fig. 1.), and apparatus for supervising the connection. Associated with the line at each end are also line circuits, the functions of which are to provide the necessary switching for the transmission and receiving ofsignals between the stations X and Y, and at the same time to disposethe apparatus so that the line is in proper condition for conversation, when the two subscribers are connected.

It is thought that the invention may be more fully comprehended from the following detailed description of the operation of the system.

Assuming that it is desired to signal station Y from station X over the transmission line L, the operator at station X will insert plug 26 of link circuit G into jack 1. A circuit is then completed from grounded battery 22, through the windin of relay 11, sleeve contacts of plug 26 an jack 1, Winding of relay 13 and winding of relay 6 to ground. As aresult of the completion of this circuit, relay 13 is actuated, but not relays 11 and 6, which are marginal. The actuation of'relay 13 causes its right-hand normal contact to open and its right-hand alternate contact to close and to'connect with conductor 20 to prepare for the subsequent short-circuiting of relay 6 over conductor 20, thereby actuating marginal relay 11 and illuminating supervisory lamp-21. Its lefthand normal contact opens, disconnecting ground from conductor 14. The operator will then actuate the key 2, disconnecting the tip and ring conductors of plug 26 from the corresponding strands of the link circuit C. At the same time the lower 'local contact of the key 2 is closed which short circuits the winding of relay 11. This short circuiting increases the current through the sleeve circuit of jack-1 and plug 26, traced above, sufficiently to cause the actuation of marginal relay 6. The actuation of this relay completes a circuit from grounded battery 22, through the windings of relays 15 and 5 in parallel, and contact of relay 6 to ground.

Both relays are energized and relay 15' through its right-hand contact connects, over conductor 25, grounded battery 23 to the plate circuit of vacuum tubes T and T,,, which starts the oscillator O. A circuit may also be traced from ground throu h source of 16-cycle ringing current 4, le thand contact of relay 15, condenser 12 and times per second, and cau'gs the generating of current waves, first of one frequency and then of another. These frequencies depend upon the particular electrical constants of p the constituent apparatus. For purposes of description, the frequencies of the currents generated may be assumed as N and N produced, respectively, by the contacts of relay 3 open and closed.

When relay 5 was actuated it disconnected the transmission line L from the tip and ring conductors connected to jack 1, and connected it to the windin s of the repeating coil Z, in serieswith which is the condenser 18. Successive trains of N and N cycle waves are now transmitted over line L to the station Y. At station Y the wave trains pass through the normal contacts of relay 105 to the incoming terminals of the'receiving circuit R The incoming waves are amplified by the amplifier circuit A and filtered by the filter circuit F. The N cycle waves, for purposes of description, may be considered as being diverted to the left-hand winding of transformer W and the N cycle waves to the left-hand winding of transformer W Tube T rectifies the N, cycle waves and tube T the N cycle waves.

The upper winding of polarized relay 107 is connected in the plate circuit of tube T and the lower winding in the plate circuit of tube T Relay 107 responds, accordingly, to the combined but not simultaneous action of the two currents. The upper winding may be assumed to be so connected that an impulse of current from the tube T will causethe upper contact of relay 107 to be closed, and that the lower winding is so connected to the tube T, that an impulse of current will cause the closureof the lower contact. Owing to the polarization of the armature of relay 107, either the upper or lower contact is normally closed, depending upon the position of the contact after the last impulse of current is received. The slow releasing relay 108 will accordingly be normally-operated from grounded battery 122, through its winding to ground at either of the normally closed-contacts of relay 107. As relay 107 receives the impulses of current from the filter F, the armature will rapidly close, the upper and lower contacts alternately, each at the rate of sixteen times per second in accordance with the frequency of the 16-cycle ringing current source 4 (Fig. 1). The actual time that each contact is closed will depend upon the armature adjustment. In general, it will he so adjusted that when the armature is vibrating at the regular 16-cycle rate, the circuit of relay 108 is rendered discontinuous for a suflicient time so that relay 108 will release and close its contact. When relay 108 has released, a circuit path may then be traced from grounded battery 122, through the left-hand winding of slow-operating relay 109, lefthand normal contact of rela 113 and contact of relay 108 to ground. is causes the actuation of relay 109 which looks up through its right-hand winding over the following path: from grounded battery 122,

through right-hand winding of relay-109,.

left-hand contact of relay 169' and righthand contact of relay 113 to ground. The actuation of relay 109 also closes a circuit from grounded battery 122, through the right-hand contact of relay 109 and lamp. 110 to ground. The illumination of lamp 110 is a signal to the operator at'stationY that station X is calling. In response to the lamp signal the operator at station Y inserts into jack 101 the plug of a link circuit similar to link circuit C. A path may then be traced over the sleeve contact of the jack 101, similar to that already traced for the sleeve circuit of jack 1 and plug 26, but including the windings of relays 106 and 113 instead of relays 6 and 13. This results in the actuation of cutofi' relay 113. Relay 109 accordingly releases and extinguishes lamp 110. Relay 113 also by its actuation completes a. path throughits left-hand alternate contact as follows: from ground, through the winding of marginal relay 106, left-hand alternate contact of relay 113, and the normally open contact of relay 108. The reason for this connection will appear from the subsequent description.

Assuming that the operator at station X has actuated a listening key 27, associated with link circuit C, the operator at stationY may thereupon ascertain the number of the desired line by the actuation of a similar listening key of the link circuit at station Y, and proceed to connect the latter link circuit with such line in the ordinary manner. The calling and called subscribers may then converse over an obvious transmission line circuit.

Assuming, while the conversation is in progress between the subscribers at station X and stat-ion Y, that the operator at station Y desires to recall the operator at station X. She will accomplish this by the actuation "of the ringing key of the link circuitiherat, which is similar to key 2 shown at station.

shown in connection with station X. The

ringing current traversing the line L to the station X will'be received by the receiving circuit, diagrammatically indicated by rectangle R,, similar to that shown at station Y, and ground will be applied to conductor 20 which will result in the short circuiting of the winding of marginal relay 6 over the following path: from ground at contact of a slow-releasing relay (corresponding to'relay 108 of receiving circuit R right-hand alternate contact of relay 13 and winding of relay 6 to'ground. This short circuiting will cause an increase in current inthe sleeve circuit, including the sleeve contacts of plug 26 and jack 1, previously traced, which will result in the actuation of marginal relay 11, which will lock up over the followingpath: from grounded battery, through the winding and left-hand alternate contactof relay 11, re-

sistance 28, and through the lefthand normal contact of listening key 27 r to ground. The supervisory lam 21'will then be illuminated from grounded attery over the right-hand alternate contact of relay 11 to ground, attracting the attention of the operator at station X. In response to the illumination of the lamp 21,the operator will connect her telephone to the line by actuating the listening key 27 thereby! opening the left-hand norma contactthereof, releasing relay 11 and extinguishing lamp 21.

The foregoing description is for a call orginating at station X and terminating at station Y. Inasmuch as the apparatus at each station is identical, it is obvious that a call may be transmitted from station Y to station X and may be handled in exactly the same way. The slow-operating line relay 9 at station X will be actuated over the following path: from grounded battery '22,.

right-hand winding of relay 9, right-hand normal contact of relay 13, conductor 20 to ground at the contact of a relay in receiver circuitR This relay corresponds to relay 108 in receiver circuit R, and is actuated in a similar manner by reason of the impulses received over the line L. Relay 9 is locked up through its left hand winding over the completion of the associated sleeve circuit,

as previously traced, and the consequent actuation of relay 1 3. The actuation of relay 13 will open the circuit through the windings of relay 9 at the normal contacts of relay 13, causing the release of relay 9 and extinguishing lamp 10.

Should the operator at station X, during the conversation between the subscribers at station X and station Y, desire to recall the operator at station Y, this can he done in the same manner as described above for the .recall of the operator at station X by the operator at station Y during the conversational period. The actuation of the ringing key at station X will cause ringing current to be transmitted to station Y and cause the short circuiting of inarginal relay 106. This will increase the current in the. sleeve circuit of the jack 101 and consequently cause the actuation of the marginal relay in the link circuit, which controls the illumination of the supervisory lamp in exactly the same manner as previously described for the lamp 21 in link circuit C.

The system described above covers a particular arrangement which has been found advantageous for signaling over toll lines eomposited for both telephone and telegraph. 'However, it will be evident to those skilled in the art that the principle of using alternately recurring-trains of electrical impulses may be applied in a number of different ways for the transmission of signals, not only through the medium of metallic wires but also through the natural media, such as earth and ether.

WVliat is claimed is:

1. In an electric signaling system, means for generating electrical impulses of different audio frequencies, a transmitting medium, a transmitting station, means thereat for applying the impulses to said transmitting medium separately and alternately in continuous succession, a receiving station, and receiving means thereat continuously connected to said transmitting medium and responsive only to the com-, binedefiect of the several electrical im-v pulses when received' singly and alternately over the transmitting medium. I 2. In an electrical signaling system, means for generating electrical impulses of different audio frequencies, a transmitting medium, a transmitting station, means thereat for applying the impulses to said transmitting medium separately and alternately, a receiving station, an amplifier circuit thereat in electrical connection with said transmitting medium, and receiving means responsive only to the combined effect of the several electrical impulses when received singly and alternately from the amplifier circuit, the circuits of. said receiving station being continuously connected to said transmitting medium.

3. In an electrical signaling system, means for generating electrical impulses of two or more audio frequencies, a transmission line, a transmitting station, means thereat for applying these impulses to said transmission line separately and alternately, a receiving station, an amplifier circuit thereat in electrical connection with said transmission line, a plurality of electrical filter circuits each tuned to one of the frequencies and electrically connected to said amplifier circuit, and receiving means associated jointly with saidfilter circuits responsive only to the combined effect of the several electrical impulses when received singly and alternately from the amplifier circuit, the circuits of said receiving station being continuously connected to said transmission line.

4. In an electrical signaling system, means for generating electrical currents of two or more audio frequencies, a transmission line, a transmitting station, means thereat for applying these currents to said transmission line separately and alternately, a receiving station, an amplifies circuit atthe receiving station in electrical connection with said transmission line, a plurality of electrical filter circuits each tuned to one of the frequencies and electrically connected to said amplifier circuit, a rectifier circuit associated with each filter circuit, and signaling means associated with the rectifier circuits responsive only to the combined effect. of the several currents when received singly and alternately from the rectifier circuits, the circuits of said receiving station being continuously connected to said transmission line.

5. In an electrical signaling system, the

combination of means for generating elec-' trical currents of two ormore frequencies, a transmission line, a, transmitting station, means thereat for applying to said transmission line said currents separately and alternately, a receiving station, an amplifier circuit at the receiving station in direct electrical connection with the transmission line, an electrical filter circuit with branches tuned to each frequency and electrically connected to said amplifier circuit, a rectifier circuit associated with each branch of said filter circuit, an electromagnetic relay with a plurality of windings, each of said windings individually associated with a branch of said rectifier circuit, and signal control means responsive to theactuationof the relay by reason of the combined energization of-the several windings.

6. In a signaling system, a telephone transmission line, signal transmitting and receiving stations associated therewith, a plurality of sources of current producing periodically varying currents in the range of audibility, means at the transmitting station for impressing upon the line recurring impulses of said currents,the impulses v mission line which comprises generating periodically varying currents of different audio frequencles, transmittlng from one point on the line recurring impulses of such currents separately and alternately, each of a predetermined duration, alternately receiving the diflerent frequency impulses at another point on the line, rectifying the im pulses andtranslating the rectified impulses into a steady signal indication, thereby se-" lectively controlling the signal indication in accordance with the frequency of the transmitted impulses, their sequence of occurrence, their duration and their period of interruption.

8. In an electrical signaling system, means for generating electric waves of two or more frequencies, a transmission line, a transmitting station, means thereat for applying the waves to said transmission line in the form of trains of predetermined sequence, duration and frequency, a receivin station and receiving means thereat continuously connected to said transmission line and selectively responsive to the combined effect due to the frequency of the trains, to their sequence of application, to their .duration and to the frequency of the constituent current waves.

9. In an electrical signaling system, means for generating electrical waves of two or more frequencies, a transmission line, a transmitting station, a source of interrupted current thereat,'a relay actuated by and in unison with said current for causing the application of the waves to said transmission line in the .form of trains of predetermined sequence, duration and frequency, a receiving station, a filter circuit thereat comprising two or more. branches, each branch corresponding to and of selectively low impedance to the frequency of a corresponding one of the current waves, and a signal control circuit electrically connected to said filtercircuit, and selectively responsi-ve to the combined effect of the frequency of the trains, of their sequence of application to the line, and of their duration.

10. In an electrical signaling system," a transmission line, a transmitting station, means for. generating a plurality of electrical impulses for signaling over said line a source of disturbing currents associated therewith, a receiving station and receiv- "ing means thereat comprising relays and filters continuously connected to said transmission line and responsive to said generated electrical impulses and. mechanically adjusted and electrically tuned to prevent its response to said disturbing currents.

11. In an electrical" signaling s stem means for generating electrical impu ses o difi'erent audio frequencies, a transmission line, a transmittin station, means thereat for applying impu ses to said transmission line separately and alternately in continuous succession,receiving means associated with said line responsive to the combined effect of the several electrical impulses each received over the transmission line, and a signal controlled by said receivin means.

12. In an electrical signa ing system, means for generatmg waves of two or more frequencies, a transmission line, a transmltting station, a source of interrupted current I thereat, a relay actuated by and in unison with said current for causing the application of the waves to said transmission line in the form of trains of predetermined sequence, duration and frequency, a receiving station, a filter circuit thereat comprising two or more branches each branch corresponding to and of selectively low impedance to the frequency of a corresponding one of said current waves, and a signal control circuit electrically connected to said filter circuit.

13. In a signaling system, a transmission line, a key, two sources of audio frequency currents, means responsive to the actuation of said key for alternately connecting said current sources to said line, means connected to the line responsive to the audio frequency currents for translating said currents into impulses of direct current, a signal, and means controlled by said impulses of direct current for actuating said signal.

14:. In a signaling system, a transmission line, a plurality of sources of currents of different frequencies, means for successively applying said frequencies to said line, a signal, an electromagnetic device for controlling said signal having a plurality of windings, a normally open circuit for each of said windings, and means associated .with said-electromagnetic device for translating the frequencies applied to said line and for completing said normally open circuits to actuate said electromagnetic device.

15. In a si naling system, a. transmission line, a. plura ity of sources of currents of different frequencies, means for successively a plying said frequencies to said line, a signa an electromagnetic device for concircuits to operate said electromagnetic derately and alternately in continuous sucvice. cession, a signal, and means including a 16. In a signaling system, means for genpolarized relay responsive to the combined 10 erating electrical impulses of different freeffect of the impulses to actuate said signal. 5 quencies, a transmission line, means for ap In witness whereof, I hereunto subscribe plying the impulses of said different fremy name this 5th day of May A. D., 1920. quencles to said transmission line sepa- PAUL B. MURPHY. 

